Study: Americans Emit 20 Metric Tons of CO2

May 05, 2008

A Massachusetts Institute of Technology class has studied the carbon emissions of Americans in a wide variety of lifestyles and estimated that people in the United States contribute much more than the global average.

"Regardless of income, there is a certain floor below which the individual carbon footprint of a person in the U.S. will not drop," says Timothy Gutowski, professor of mechanical engineering, who taught the class that calculated the rates of carbon emissions. The results will be presented in May at the IEEE International Symposium on Electronics and the Environment in San Francisco.

While it may seem surprising that even people whose lifestyles don't appear extravagant--the homeless, monks, children--are responsible for significant greenhouse gas emissions, one major factor is the array of government services that are available to everyone in the United States. These basic services--including police, roads, libraries, the court system and the military--were allocated equally to everyone in the country in this study. Other services that are more specific, such as education or Medicare, were allocated only to those who actually make use of them.

The students conducted detailed interviews or made detailed estimates of the energy usage of 18 lifestyles, spanning the gamut from a vegetarian college student and a 5-year-old up to Oprah Winfrey and Bill Gates. The energy impact for the rich was estimated from published sources, while all the others were based on direct interviews. The average annual carbon dioxide emissions per person, they found, was 20 metric tons, compared to a world average of 4 tons.

But the "floor" below which nobody in the U.S. can reach, no matter a person's energy choices, turned out to be 8.5 tons, the class found. That was the emissions calculated for a homeless person who ate in soup kitchens and slept in homeless shelters.

The analysis was carried out by Gutowski and 21 students in his 2007 class, "Environmentally benign design and manufacturing." They developed a system for making such comparisons, which they call ELSA--environmental life style analysis.

The students looked at the factors within each person's control that might lead to a reduction in carbon output. They found that achieving significant reductions for the most part required drastic changes that would likely be unacceptable to most people. As a result, they said, "this all suggests to us very significant limits to voluntary actions to reduce impacts, both at a personal level and at a national level."

The biggest factors in most people's lives were the obvious energy-users: housing, transportation and food. "The simple way you get people's carbon use down is to tax it," Gutowski says. "That's a hard pill to swallow--politicians don't like to step up" to support such measures. Absent such national actions, he says, it is important to study "what role consumer choices can play" in lowering the nation's carbon emissions.